Amphibians
Sierran Treefrog
Pseudacris sierra · also called Sierran treefrogs, Sierran chorus frog
Clinging to a blade of grass near a Central Valley pond, a Sierran treefrog shifts its colouration between green and brown, a species that spent years lumped together with relatives to the north and south before genetic study finally recognised it as its own distinct species.
Overview
The Sierran treefrog, Pseudacris sierra, is a small, colour-shifting amphibian native to a wide range of habitat, including forest, grassland, and wetland edges, across central California, including the Central Valley and Sierra Nevada foothills. Its relatively recent recognition as a species distinct from the broader Pacific treefrog group, ability to shift between green and brown colouration, and strong tolerance for disturbed and suburban habitat make it one of the more adaptable and taxonomically interesting small frogs in California.
A species that was hiding within a wider one
For a long time, what is now called the Sierran treefrog was simply lumped in with a far more broadly defined Pacific treefrog, until genetic study drew a line through California and revealed several separate species where scientists had once seen only one.
Status
Least Concern — widespread and abundant across suitable habitat throughout central California, aided by a strong tolerance for disturbed and suburban conditions.
Sierran Treefrog: common questions
Is the Sierran treefrog the same as the Pacific chorus frog?
They are close relatives that were once considered the same species; genetic study has since split what was long treated as a single, wide-ranging Pacific treefrog into several separate species, with the Sierran treefrog centred on California's Central Valley and Sierra Nevada while the more narrowly defined Pacific chorus frog occupies a different part of the range farther north.
Can the Sierran treefrog change colour?
Yes, this species can shift its skin colour between green and brown depending on temperature, humidity, and the colour of its surroundings, a degree of colour change more pronounced than in many other frog species and useful for blending into varied backgrounds.
Why does the Sierran treefrog do so well in disturbed and suburban habitat?
This species is a generalist that breeds readily in almost any shallow, fish-free water, including artificial sites such as ditches, tyre ruts, and flooded fields, and tolerates a wide range of temperature and moisture conditions, allowing it to persist in disturbed and suburban habitat where more specialised frog species often disappear.
How can you identify a Sierran treefrog?
Look for a dark stripe running through the eye, combined with the species' ability to shift between green and brown colouration and its adhesive toe pads suited to climbing, though since this species looks very similar to several close relatives from the same recent taxonomic split, range is also an important clue for confirming identification.